unbalanced neutral

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PhaseShift said:
The diagram that is confusing me is the one attached. These represent the two different cases where the grounding electrode and system bonding jumper are located at different locations for a SDS. In these diagrams what are the conductors that I have questioned? Are these the EBJ's that were referenced?
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The point the diagram is trying to make is you should bond the groundED and groundING (neutral & equipment ground) at only one point or you risk creating parallel return paths. The diagram actually shows the two possible paths with directional arrows on the conductors. As stated by smart as well as the diagram itself this case is definitly a seperately drived system. Try reading the NEC250 a few more times. I know it's a lot to take it when you read it all at once but after the 10th-20th time it all starts to me sense ;).
 
skeshesh said:
The point the diagram is trying to make is you should bond the groundED and groundING (neutral & equipment ground) at only one point or you risk creating parallel return paths. The diagram actually shows the two possible paths with directional arrows on the conductors. As stated by smart as well as the diagram itself this case is definitly a seperately drived system. Try reading the NEC250 a few more times. I know it's a lot to take it when you read it all at once but after the 10th-20th time it all starts to me sense ;).
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Starting to make a little more sense.

So the groundED conductor above is the neutral conductor and the groundingING conductor above is the equipment bonding jumper as you are refereincing it? So it looks like for a SDS that these two should only be bonded (system bonding jumper) at only one place to avoid parallel neutral return paths. I guess it does not matter either if the grounding electrode is at both locations as long as the system bonding jumper is only in one or the other location.

It also looks like you are saying that the EBJ is required for both cases for a SDS. Is this EBJ typically run with POCO connections between transformer and meter?

Seeing that this EBJ is required for all SDS's then you should always have (4) wires (2) hot, (1) neutral, (1) EBJ between SDS and panel?

Also referenced was a service. Is this not necessarily a SDS but can be from any source (panel, mcc, etc..) to a building service? This will always require an EGC? What about an EBJ?

Almost have it all
 
PhaseShift said:
Starting to make a little more sense.

So the groundED conductor above is the neutral conductor and the groundingING conductor above is the equipment bonding jumper as you are refereincing it? So it looks like for a SDS that these two should only be bonded (system bonding jumper) at only one place to avoid parallel neutral return paths. I guess it does not matter either if the grounding electrode is at both locations as long as the system bonding jumper is only in one or the other location.
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EBJ is a grounding conductor on the line side of the system disconnecting means.

The GEC is required to be "bonded" to the grounded conductor at the same location as the system bonding jumper.

It also looks like you are saying that the EBJ is required for both cases for a SDS. Is this EBJ typically run with POCO connections between transformer and meter?
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No.

Seeing that this EBJ is required for all SDS's then you should always have (4) wires (2) hot, (1) neutral, (1) EBJ between SDS and panel?
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The EBJ is not required to be a wire. It can be any in the list of grounding conductor types.

Also referenced was a service. Is this not necessarily a SDS but can be from any source (panel, mcc, etc..) to a building service? This will always require an EGC? What about an EBJ?
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A service is distinguished from an SDS in that the POCO owns the transformer which is outside the NEC's purview. The secondary conductors may or may not be within the NEC's purview. Regardless, if there is a grounded secondary conductor, it is bonded to the equipment, the distribution ground/neutral, and likely a grounding electrode. For this reason, a grounding conductor is not run to the service because it would create a parallel path for current intended to be carried by the grounded conductor when you bonded it per NEC. On occasion the service conductors are run in bonded metal conduit (such as when required to be protected against physical damage), but the conduit is usually isolated at one end or the other.
 
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Smart $ said:
A service is distinguished from an SDS in that the POCO owns the transformer which is outside the NEC's purview. The secondary conductors may or may not be within the NEC's purview. Regardless, if there is a grounded secondary conductor, it is bonded to the equipment, the distribution ground/neutral, and likely a grounding electrode. For this reason, a grounding conductor is not run to the service because it would create a parallel path for current intended to be carried by the grounded conductor when you bonded it per NEC. On occasion the service conductors are run in bonded metal conduit (such as when required to be protected against physical damage), but the conduit is usually isolated at one end or the other.
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It sounds like sometimes the EBJ may be an actual wire, however other times it is not, and this grounding conductor is not run to the serive. If it is not run to the service, then how is the required EBJ requirement met?

So since everything we talked about above deals between a SDS and the first serivce point (panel, disconnect, etc..) then at what point does an EGC come into play? Would the EGC be required for everything after this initial service point?
 
PhaseShift said:
It sounds like sometimes the EBJ may be an actual wire, however other times it is not, and this grounding conductor is not run to the serive. If it is not run to the service, then how is the required EBJ requirement met?
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An EBJ is not always required for a service. In most instances, the grounded conductor, should there be one, is used to ground enclosures on the line side of the service disconnecting means. If you have a ungrounded service, you would have to run EBJ's for grounding.

So since everything we talked about above deals between a SDS and the first serivce point (panel, disconnect, etc..) then at what point does an EGC come into play? Would the EGC be required for everything after this initial service point?
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You'd be better off not calling it the first "service point", which has a specific meaning in NEC terminology. When you are talking code, it is less confusing if you use code terminology. Better to call it a service or system disconnecting means (field lingo: main or sub, switch, disconnect, cut out, etc. with several combos and variations). Note the latter covers both a service and an SDS, but the former covers only the "service".

EGC's are on the load side of the system disconnecting means. EBJ's are on the line side... usually. The exception(s?) would be for example a generator with integral disconnect/ocpd.
 
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Smart $ said:
. In most instances, the grounded conductor, should there be one, is used to ground enclosures on the line side of the service disconnecting means.
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O.k. I think it all makes sense now! Thanks :grin:

One last question: In your response above is the "grounded conductor" you are referring to the same as the neutral?
 
Just to hammer this home once and for all I wanted to understnad this be sketching the two scenarios for the two methods discussed above both using a sepeare wire for the EBJ, and using the Grounded Wire as the EBJ.

In the top sketch, this shows the wire labeled (2) as being a 4th wire pulled between the transformer and panel used as the EBJ.

In the bottom sketch this shows the grounded wire (1) as being used for both the grounded wire (neutral) and the EBJ

Have I represented these two cases correctly?

I guess it does not matter which method is used or if one prefered over the other. My only thought is that the latter example would be cheaper.
 
FWIW, I've never seen case #1.

Being we are talking service configurations, case #2 would have a grounding electrode (rod, usually; sometimes grounding grid or ring) bonded to the grounded conductor (neutral, in this case) and transformer frame/enclosure.
 
FWIW, I've never seen case #1.[/QUOTE]

I guess I am used to working in an industrial enviornment where I see typically a green and white wire carried from the transformer to the panel or disconnect. In this case you should only have a system bonding jumper at one location as mentioned above.


Smart $ said:
Being we are talking service configurations, case #2 would have a grounding electrode (rod, usually; sometimes grounding grid or ring) bonded to the grounded conductor (neutral, in this case) and transformer frame/enclosure.
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Like I said I'm used to SDS's in an industrial setting so I guess I dont typically see this although you may be right. If we just use the one grounded wire then we can have a ground electrode at both ends as you mentioned. I guess even if we had two wires we can still have a electrode at both ends as long as there is only a system bonding jumper at one location.
 
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